The present invention is directed to a photographic developer composition for processing radiographic silver halide emulsions in automatic film processors, which does not contain any toxic chemicals (as deemed advisable by the Occupational Safety and Health Act) and does not contain any substances deemed hazardous to the environment under Title III of the Superfund Amendments and Reauthorization Act of 1986 (SARA), Sections 302, 304, and 313.
Photographic developer compositions for radiographic materials are well-known in the art. The processing of silver halide photographic materials is performed by a multiple step sequence consisting of developing, fixing, washing and drying steps. The development step is conventionally undertaken with an aqueous alkaline developer composition containing hydroquinone as a developing agent either singly or with one or more additional developing agents.
More specifically, the exposure of a silver halide emulsion to radiation to which the emulsion is sensitized produces a latent image in the silver halide grains of the emulsion. The latent image is developed by immersion of the exposed emulsion into an aqueous developing solution which contains a reducing (developing) agent. The hydroquinone or other suitable developing agent serves to reduce the exposed silver halide grains to yield the developed photographic image.
In radiographic applications, the materials normally have a silver halide emulsion on both sides, which presents specific problems when these materials are developed in automatic, roller-type processors. The higher heat of development (customarily 90.degree. to 95.degree. F.) softens these emulsions, making them very susceptible to being scratched during development and transport between tanks. In addition, the softened emulsions absorb additional moisture as they become swollen, making it very difficult to remove enough moisture to adequately dry the film before it exits from the processor. For this reason many hardening agents have been explored for inclusion in the developer composition to reduce swelling (softening) of the emulsion during development. In practice, an aldehyde such as formaldehyde or glutaraldehyde or a bisulfite adduct of these is commonly used. The preferred compound is glutaraldehyde which hardens better in the presence of sulfite (which is normally included in a developer composition as a preservative for developing agents) than formaldehyde (see, Photographic Processing Chemistry, L. F. A. Mason, 1966, p. 154).
While hydroquinone-based developer compositions containing a dialdehyde have been employed with success for many years, more recently the use of such compositions has met with some doubt due to the toxicity and hazardous impact on the environment of hydroquinone, caustic alkalies, and dialdehydes such as glutaraldehyde. That is, due to the toxic nature of various components employed in conventional radiographic developer compositions, it is necessary to meet various guidelines and regulations promulgated to protect either the health of those who are exposed to such compositions or to protect the environment into which such compositions are exposed. As three of the least desirable components generally present in conventional radiographic developer compositions are hydroquinone, caustic alkalies, and glutaraldehyde, it would thus be desirable to discover acceptable substitutes which are less toxic by nature.
It is also important to maintain the pH of the developer composition within strict alkaline ranges to ensure satisfactory and consistent operation of the composition. For this purpose, caustic alkalies (caustic soda or caustic potash) are normally employed in the developer composition.
Exemplary hydroquinone-based developer compositions are disclosed in, for example, U.S. Pat. Nos. 2,893,865; 3,733,199; 3,865,591; 4,046,571; 4,205,124; 4,756,990; and 4,816,384.